Electric heating element assemblies are used in a variety of applications, including heat exchangers, circulation systems, steam boilers, and immersion heaters. An electric heating element assembly generally includes a sheath, dielectric insulation within the sheath, an electrical resistance coil embedded in the dielectric insulation, and a conductor pin extending from the electrical resistance coil. Voltage is supplied to the conductor pin to generate heat in the electrical resistance coil. Many applications and systems that include electric heating element assemblies are rated for low voltage operations, where voltages below 600 volts can be considered low voltages. For example, many current heat exchangers operate with voltages in the range of 480 to 600 volts. More recently, various applications and systems for electric heating element assemblies have been proposed that operate above 600 volts. For example, heat exchangers that operate in the range of 600 to 38,000 volts have been proposed. These higher capacity heat exchangers are proposed as environmentally friendly alternatives to fuel-based heat exchangers. Voltages between 600 and 38,000 can be considered medium voltages. These higher voltages can place greater demands on the electric heating element assemblies.
For example, the higher voltage can be more difficult to dielectrically insulate, particularly at interfaces between the various components of the electric heating element assembly. The dielectric insulation within the sheath can include a single row of longitudinally-arranged dielectric cores, for example, which can be positioned end-to-end. Furthermore, a terminal bushing can be positioned against a dielectric core of the electric heating element assembly. At the interfaces between adjacent dielectric cores and/or between the terminal dielectric core and the bushing, higher voltages can be difficult to dielectrically insulate and, in some instances, dielectric breakdown and/or arcing can occur.